In my universe, FTL communication using entanglement SEEMS to have been achieved. I understand quite well from a layman's perspective how it's basically impossible without a complete overhaul of established physics. But since it's based on a far-fetched speculation, never turned into reality in the universe of my story, what possible alterations to physics could scientists postulate?
4$\begingroup$ At this point, asking how to change physics to introduce FTL is the same as asking, "What magic system should I create?" If you TELL us what change you're making to physics, we can postulate results, but it is absurd to ask what change because that means literally everything has to go out the window. And that is a Too Broad question in my book. $\endgroup$– SRMJan 29, 2017 at 9:42
1$\begingroup$ What do you mean by saying that FTL communication seems to have been achieved? Can you give an example? $\endgroup$– AlexPJan 29, 2017 at 12:01
$\begingroup$ @SRM No, not everything has to go out the window. If it's quantum entanglement, then something like the Einstein-Podolsky-Rosen (EPR) paradox has to be non-paradoxical. Physics is doubtless robust enough to survive losing locality. It may be too broad in your book, some of us have extra chapters in our volumes. The OP is only looking for a plausible explanation. Plausibility doesn't need to be confused with realism. $\endgroup$– a4androidJan 29, 2017 at 12:05
$\begingroup$ Ah ha! Having seen comments below it obvious you're looking for scientific explanations for what seems like FTL communication. When the situation is more like the FTL neutrino false results at CERN. This unleashed a torrent of possible explanations from theoreticians. You must understand theoreticians are like that. So this would be a similar situation. $\endgroup$– a4androidJan 29, 2017 at 12:22
1$\begingroup$ @a4android Great. You picked a magic system. Now we can discuss the ramifications of throwing out locality. There are other ways to do it. The question is NOT asking about locality. It is asking for an open list of ways to change physics. Mithrandir's answer (as you proposed) is a good answer, but it is also a perfect example to me of why this is a poorly thought out question. $\endgroup$– SRMJan 29, 2017 at 17:17
This is a use of the Quantum Mechanics Can Do Anything ⚠trope, and a “groaner” to an increasingly large number of readers.
The idea of corralation of distant observations emerges from the math of non-separable states. You can't just put nonlocal communication in without messing up the foundations of QM. So you can’t make a simple alteration to physics to make changes to one entangled particle cause its mate to be changed, as opposed to breaking the entanglement.
It makes for a smarter story to introduce a new, different effect, and give it any properties you want. For example, in The Metamorphosis of Prime Intellect, the “correlation effect” was clearly something different, and discovering it changed the universe.
If you’re looking for ideas in general, not trying to make QM do this, see Is there a scientifically plausible faster-than-light communication system? , Science-based FTL drive, Are there any ways to allow some form of FTL travel without allowing time travel?, and others already posted here.
$\begingroup$ Myabe I should have been clearer. I'm not asking "how to make FTL entanglement communication work in my universe". In the story, it NEVER works. It's not that in the world, "Quantum Mechanics Can Do Anything". "You can't just put nonlocal communication in without messing up the foundations of QM." Exactly what my question was about: "what possible alterations to physics..." $\endgroup$ Jan 29, 2017 at 8:32
$\begingroup$ Alterations that don’t allow FTL? Then whats to change? $\endgroup$ Jan 29, 2017 at 8:40
$\begingroup$ "Exactly what my question was about", in that in my world, your statement "you can't just put nonlocal communication in without messing up the foundations of QM" is true. Hence the word "seems" in all caps in my question. I wanted to put some weight on the fact that this is a qualitatively different question from "how to make entanglement-based FTL communication work in my world", since I knew that question has been asked before. $\endgroup$ Jan 29, 2017 at 9:11
2$\begingroup$ How does it seem to be FTL when it never works as such? $\endgroup$ Jan 29, 2017 at 9:13
By the Principle of Locality, this is impossible with currently known physics. As such, this might be one of the first things to be questioned.
Alternatively, it would be possible if something like wormholes were discovered, which would mean that it would be possible to warp spacetime to a large enough degree so that 2 arbitrarily far away points could be brought close together and what appears to be FTL communication could occur - that is, nothing's actually travelling faster than light, only space is being manipulated so that the 2 points are temporarily brought closer together and so, during that time, regular communications don't take as long.
Now, back in 2011, physicists thought that they had measured neutrinos travelling faster than light (it turns out that they just made an experimental error), but as a result of this, lots of papers (almost 200) popped up about how this might be possible. This list can be found here - if you want to read a paper, you need to open the link to arXiv, then remove the following part of the URL: "web.archive.org/web/[number]/".
A small number of examples of explainations are:
- An acceleration due to gravity
- Another fundamental speed limit > $c$
- Extra dimensions
- a result of Neutrino mixing
While accelerations due to gravity and neutrino mixing don't affect photons, if a classical signal could be sent faster than light (i.e. if neutrinos could travel faster than light), this would allow for communication-by-entanglement that is faster than light as a classical signal needs to be sent at some point in order for communication-by-entanglement to work.
$\begingroup$ That list of papers you cite? That results from the first magic of proposing it is nutrinos that go faster than light. If question wants to propose that change, go for it. Right now, the question as phrased is just as validly answered by "assume we are in a simulated universe where code injection from the outside is possible." Or any other magic system. $\endgroup$– SRMJan 29, 2017 at 17:21
$\begingroup$ The OP noted on the first posted Answer, «I'm not asking "how to make FTL entanglement communication work in my universe". In the story, it NEVER works» so this Answer seems to have the same issue. That is, we don’t really know what the OP was asking. $\endgroup$ Jan 29, 2017 at 21:07
1$\begingroup$ To me, the OP is saying that there seems to be an event that appears to be FTL communication, only it's not actually FTL communication (maybe just a coincidence or error in calculation). The OP then goes on to ask "what possible alterations to physics could scientists postulate?" - hence the comparison with the neutrinos seeming to go FTL, which is as close to the proposed scenario as has happened so far on Earth. The list of papers is a major part of the 'could be postulated' as that was what was postulated when a similar event actually happened $\endgroup$ Jan 29, 2017 at 21:27
$\begingroup$ @Mithrandir24601 "To me, the OP is saying that there seems to be an event that appears to be FTL communication, only it's not actually FTL communication (maybe just a coincidence or error in calculation)." - This exactly. $\endgroup$ Jan 30, 2017 at 9:14
Its hard to say what theories science will come up with without data, and obviously you're not about to give us a pile of fake data to analyze =) Science builds models to fit the data, so it won't do anything without them.
However, there are two very general directions scientists are likely to turn. The first is the topology of space. There would probably be at least a few theories suggesting space is getting bent or even tied into knots. The other approach would probably involve particles that travel faster than light. The "Atomic Principle" is very popular these days. This principle is an unprovable hypothesis that the entire universe can be fully understood as a set of indivisible objects, each of which has some state. This approach is very popular in the subatomic physics world, so I would expect many theoretical physicists to explore this direction.
Of course, it could get more complicated if we figure out how to apply this principle before we fully understand it. Then all sorts of interesting patterns may emerge, such a papers claiming Bumblebees can't fly because their wing to weight ratio isn't high enough.
FWIW, it is much easier to conceive of plausible beyond general relativity and Standard Model physics that would allow for FTL communication than it is to imagine any plausible means by which FTL travel would be possible.
For example, one fairly mainstream (although minority) school of thought on how we can solve the unsolved problem of quantum gravity in physics is called "loop quantum gravity."
In loop quantum gravity, the very concept of "locality" is an emergent phenomena. Fundamentally, in LQG, there are a bunch of points in space-time connected to a bunch of other points in space-time, and when those form networks that cluster together, you get an emergent sense of locality based on the average number of hops to get from points with close connections to point A to points with close connections to point B.
But, nothing in loop quantum gravity prevents a few stray connections between space-time points from connecting directly to point C which has an average number of hops to reach point A that is much, much greater than point B.
One possible connection to this concept in quantum mechanics comes from the propagator function for the photon.
You see, in Quantum Electrodynamics (QED), the probability of a photon going from point A to point B at a certain time in the future, is determined by considering all possible paths from point A to point B, including paths upon which the photon travels at slightly less than the speed of light or slightly more than the speed of light, although the greater the deviation from the speed of light, the less probable it is that a photon will take that path. If you only consider paths at exactly the speed of light when calculating the probability that a photon will end up at a particular place and time in the future, you will get the wrong answer.
One "realist" interpretation of this empirical fact about the photon propagator. Photons really move a fixed number of hops per second, but it reflects the LQG concept that locality is emergent and that the distance from point A to point B reflects merely the average number of hops across space-time points that it takes to get from point A to point B, even though different paths may actually involve moderately different numbers of hops, and in highly improbable circumstances, very different numbers of hops.
Thus, fundamental particle sized wormholes, rather than being the exception, are the fundamental nature of space-time from which an apparently continuous and smooth apparent space-time emerges because the number of hops involved in any macroscopic trip from a point A to a point B is so great that the law of averages obliterates any apparent distinctions due to random variations in the number of hops necessary to cross a particular small distance.
Since these non-local connections are ubiquitous, finding local ones that connect to distant places in the universe isn't necessarily so hard. But, the problem is bandwidth. A non-local connection could support only one fundamental particle (such as a photon) at a time. This works great for communication but is lousy for moving solid, macroscopic objects.
$\begingroup$ «FWIW, it is much easier to conceive of plausible beyond general relativity and Standard Model physics that would allow for FTL communication than it is to imagine any plausible means by which FTL travel would be possible.» I think they are exactly the same. Travel of objects is just a special case with the real issue being causality. $\endgroup$ Jan 30, 2017 at 7:18
$\begingroup$ IAC, proposing plausible FTL mechanisms is espressly not what the OP is after. This would make a good answer for this question though. $\endgroup$ Jan 30, 2017 at 7:22
$\begingroup$ Not really. Lots of "FTL" concepts (including the one above) involve messing around with the topology of space-time in a manner such that apparent distance by the ordinary route, and actual distance, are different, and it doesn't actually involve traveling faster than light, its really just a short cut. This doesn't raise the causality issues of truly superluminal phenomena, and it is easier to imagine such topological defects at a micro-scale than at a macro-scale. In entanglement terms a similar conjecture is called EPR=ER. quantumfrontiers.com/2013/06/07/entanglement-wormholes $\endgroup$ Jan 30, 2017 at 7:24